Not sure if this has been posted before but I was listening to a science podcast (Infinite Monkey Cage) the other day and they were talking about the brain. One of the panellists mentioned that there was a group a nuns who donated their brains to medical research and it transpired that many of them had indicators of Alzheimers despite showing no symptoms. It was posited that by keeping positive and busy, the brain compensated for the damaged areas.
Nun Study - Wikipedia
en.wikipedia.org